This invention relates to an electric motor driven wheel and more particularly to an improved, compact electric motor for driving such a wheel.
A wide variety of vehicles are provided with electric motors for their drive. In one preferred form of such arrangement, the electric motor is incorporated into a part of the wheel construction so as to provide a very compact arrangement. That is, it is desirable to make the electronic motor compact enough so that it can be nested at least in part into the wheel so as to provide a neat and yet highly serviceable assembly.
Generally, the electric motor includes a rotor and a stator, one of which carries a plurality of permanent magnets and the other of which carries a plurality of electrical coils that cooperate with the magnets. Electrical power is delivered to the coils in sequential fashion so as to effect rotation of the rotor and this rotation is used to drive the wheel.
Normally, the flow of current through the electrical coils is controlled by an electric power control for sequentially energizing the coils and this is in the form of an electrical power controlling inverter that is formed of a plurality of FETs"" that switch the power supply to the coils. The inverter is generally arranged so that the switching elements such as the FETs"" are mounted on a substrate. In addition, charging capacitors, current detecting sensors and power supply cables for sending and receiving signals between the controllers and a CPU are connected to the various terminals on the substrate. However, with this type of arrangement, the switching action of the FETs"" causes them to develop heat and further heat is generated from the coils of the electric motor. If the construction is compact, the heat generated can cause some problems and thus, previously proposed systems have not been as compact as desired.
It is, therefore, a principal object to this invention to provide an improved and compact electric motor for driving a wheel wherein the motor elements are arranged so that the controller is well insulated from the heat generated by the motor operation.
In connection with such electric motor driven wheels, the output of the electric motor generally is such that it is desirable to include an arrangement that incorporates a speed changing transmission for increasing the torque at lower speeds and loads and for permitting high speed operation as the vehicle has been accelerated. Obviously, it is difficult with such compact constructions to incorporate such a transmission mechanism and the control for it.
It is, therefore, a still further object to this invention to provide an improved and compact transmission arrangement for use integrally with an electric motor for driving a wheel and providing a compact construction.
In addition to the necessity for a transmission, it is also generally the practice to provide some type of brake for the electric motor driven wheel. It is particularly advantageous if this brake can be incorporated into the electric driving motor, however this still aggravates the problem in maintaining a compact construction.
An advantage with incorporating the brake within the driving motor is that it eliminates the need for having a separate braking element that is fixed to the wheel and the associated frictional mechanism for braking this rotating member.
It is, therefore, a still further object to this invention to provide an improved and compact electric motor for driving a wheel that incorporates a braking system within it.
The various features of this invention are adapted to be embodied in an electric motor arrangement for driving an associated, juxtaposed wheel. The electric motor is comprised of a rotor and a stator, which are supported for relative rotation. One of rotor and stator carry a plurality of spaced permanent magnets and the other carries a plurality of coil windings that are juxtaposed to the permanent magnets for effecting rotation of the rotor. A motor cover encloses the rotor and the stator and is adapted to extend at least in part into the associated wheel.
In accordance with a first feature of the invention, a wheel driving shaft is driven by the rotor and has an end portion extending through an opening in the motor cover for driving the associated wheel. The motor cover opening is surrounded by a disk shape portion and a controller for controlling the supply of electric power to the coils is mounted on the side of the disk shape portion through which the wheel driving shaft extends.
In accordance with a second feature of the invention, the rotor is comprised of a cup shape member having a cylindrical portion closed at one end by a circular end wall through which the wheel driving shaft passes. A first reduction gear set is provided on one side of the circular end wall for driving the wheel driving shaft from the rotor at a first speed ratio and is disposed axially within the cylindrical portion. A second reduction gear set is disposed on the other side of the circular end wall for the driving wheel driving shaft from the rotor at a second speed ratio that is different from the first speed ratio.
In accordance with yet a third feature of the invention, the wheel driving shaft has a first end portion that extends through an opening in one side of the motor cover for driving the associated wheel. The wheel driving shaft has a second portion extending through an opening in the other side of the motor cover and a braking device is associated with the wheel driving shaft second end portion for braking the rotation of the wheel driving shaft and the associated wheel.